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C. Mudry

Publications and source records attributed to C. Mudry.

26 records · Page 2Linked to original sources
arXiv2001

Fokker-Planck equations and density of states in disordered quantum wires

We propose a general scheme to construct scaling equations for the density of states in disordered quantum wires for all ten pure Cartan symmetry classes. The anomalous behavior of the density of states near the Fermi level for the three chiral and four Bogoliubov-de Gennes universality classes is analysed in detail by means of a mapping to a scaling equation for the reflection from a quantum wire in the presence of an imaginary potential.

cond-mat.dis-nn↗
arXiv2000

Localization and delocalization in dirty superconducting wires

We present Fokker-Planck equations that describe transport of heat and spin in dirty unconventional superconducting quantum wires. Four symmetry classes are distinguished, depending on the presence or absence of time-reversal and spin rotation invariance. In the absence of spin-rotation symmetry, heat transport is anomalous in that the mean conductance decays like $1/\sqrt{L}$ instead of exponentially fast for large enough length $L$ of the wire. The Fokker-Planck equations in the presence of time-reversal symmetry are solved exactly and the mean conductance for quasiparticle transport is calculated for the crossover from the diffusive to the localized regime.

cond-mat.mes-hall↗
arXiv1999

Nonuniversality in quantum wires with off-diagonal disorder: a geometric point of view

It is shown that, in the scaling regime, transport properties of quantum wires with off-diagonal disorder are described by a family of scaling equations that depend on two parameters: the mean free path and an additional continuous parameter. The existing scaling equation for quantum wires with off-diagonal disorder [Brouwer et al., Phys. Rev. Lett. 81, 862 (1998)] is a special point in this family. Both parameters depend on the details of the microscopic model. Since there are two parameters involved, instead of only one, localization in a wire with off-diagonal disorder is not universal. We take a geometric point of view and show that this nonuniversality follows from the fact that the group of transfer matrices is not semi-simple. Our results are illustrated with numerical simulations for a tight-binding model with random hopping amplitudes.

cond-mat.dis-nn↗
arXiv1999

Density of states in coupled chains with off-diagonal disorder

We compute the density of states (d.o.s.) in N coupled chains with random hopping. At zero energy, the d.o.s. shows a singularity that strongly depends on the parity of N. For odd N, the d.o.s. is proportional to 1/(E (\ln |E|)^3), with and without time-reversal symmetry. For even N, the d.o.s. is proportional to \ln |E| in the presence of time-reversal symmetry, while there is a pseudogap, d.o.s. proportional to E \ln |E|, in the absence of time-reversal symmetry.

cond-mat.dis-nn↗
arXiv1998

Delocalization in coupled one-dimensional chains

A weakly disordered quasi-one-dimensional tight-binding hopping model with $N$ rows is considered. The probability distribution of the Landauer conductance is calculated exactly in the middle of the band, $ε=0$, and it is shown that a delocalization transition at this energy takes place if and only if $N$ is odd. This even-odd effect is explained by level repulsion of the transmission eigenvalues.

cond-mat.dis-nn↗
arXiv1996

The Liouville Theory as a Model for Prelocalized States in Disordered Conductors

It is established that the distribution of the zero energy eigenfunctions of (2 + 1)-dimensional Dirac electrons in a random gauge potential is described by the Liouville model. This model has a line of critical points parameterized by the strength of disorder and the scaling dimensions of the inverse participation ratios coincide with the dimensions obtained in the conventional localization theory. From this fact we conclude that the renormalization group trajectory of the latter theory lies in the vicinity of the line of critical points of the Liouville model.

cond-mat↗
arXiv1994

The mechanism of spin and charge separation in one dimensional quantum antiferromagnets

We reconsider the problem of separation of spin and charge in one dimensional quantum antiferromagnets. We show that spin and charge separation in one dimensional strongly correlated systems cannot be described by the slave boson or fermion representation within any perturbative treatment of the interactions between the slave holons and slave spinons. The constraint of single occupancy must be implemented exactly. As a result the slave fermions and bosons are not part of the physical spectrum. Instead, the excitations which carry the separate spin and charge quantum numbers are solitons. To prove this {\it no-go} result, it is sufficient to study the pure spinon sector in the slave boson representation. We start with a short-range RVB spin liquid mean-field theory for the frustrated antiferromagnetic spin-${1\over2}$ chain. We derive an effective theory for the fluctuations of the Affleck-Marston and Anderson order parameters. We show how to recover the phase diagram as a function of the frustration by treating the fluctuations non-perturbatively.

cond-mat↗